Methanesulfonic acid
chemical compound
Methanesulfonic acid (MsOH, MSA) is an organosulfuric, colorless liquid with the molecular formula CH3SO3H and structure H3C−S(=O)2−OH. It is the simplest of the alkylsulfonic acids (R−S(=O)2−OH). Salts and esters of methanesulfonic acid are known as mesylates (or methanesulfonates, as in ethyl methanesulfonate). It is hygroscopic.
History and synthesis
Early history
German chemist Hermann Kolbe discovered MSA between 1842 and 1845 and originally termed it methyl hyposulphuric acid.
The discovery stemmed from earlier work by Berzelius and Marcet in 1813, who treated carbon disulfide with moist chlorine and produced a compound they named "sulphite of chloride of carbon". By reacting it with barium hydroxide Kolbe demonstrated it to actually be trichloromethylsulfonyl chloride (CCl3SO2Cl).
2 CCl3SO2Cl + 3 Ba(OH)2 → Ba(CCl3SO3)2 + 3 BaCl2 + 2 H2O
From resulting barium trichloromethylsulfonate Kolbe isolated the free acid, which he was then able to sequentially dechlorinate by electrolytically generated atomic hydrogen to ultimately yield MSA.
CCl3SO3H + 3 H → CHCl2SO3H + 2 H + HCl → … → CH3SO3H + 3 HCl
Kolbe's research on methanesulfonic and chloroacetic acids was hailed by Berzelius as strong evidence for his theory of copulated compounds, a modification of radical theory to accommodate substitution reactions which posited the combination of organic and inorganic moieties without significantly altering the properties of the latter.
Later in the 19th century, the name transitioned to methyl sulphonic acid. Other historical laboratory synthesis routes included oxidizing methanethiol, dimethyl disulfide or methyl thiocyanate with nitric acid.
Industrial production
The first commercial production of MSA, developed in the 1940s by Standard Oil of Indiana, was based on oxidation of dimethylsulfide by O2 from air.
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